COMMENTARY | EPA’s Seresto Decision is Harmful to Your Pet

Kyla Bennett

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EPA’s Seresto Decision is Harmful to Your Pet

Back in 2012, the U.S. Environmental Protection Agency approved the popular Seresto pet collar to control fleas, ticks, mosquitoes, and other pests. Almost immediately, EPA started receiving “incident reports” from the manufacturer (in this case, from Bayer, one of the largest – and most infamous – pharma and biomedical companies in the world, which sold its animal health line to Elanco in 2020).

These reports did not just trickle in – they flooded in. By 2022, EPA had received more than 100,000 incident reports about the collars, including 2,500 pet deaths. These reports included several hundred human health events with stricken pet owners calling into poison centers.

While most of the incidents with dogs and cats involved skin effects, such as rashes, more than one-third involved multiple organ systems, such as convulsions, muscle tremors, and loss of control of bodily movements. Other reported effects included lethargy, abnormal behavior, excessive grooming and vocalization, vomiting, diarrhea, and anorexia.

Based on its review of U.S. incidents and toxicology studies, Canada’s Pest Management Regulatory Agency concluded that the collar posed too great a risk to pets and their owners to be sold in Canada. Canada took that action in 2016.

By contrast, EPA did nothing.

EPA could have ordered the Seresto collars off the market, as Canada did, but it made no move to do so even as its own analysis of incidents concluded that of all flea and tick products in EPA’s Incident Data System, “Seresto ranked #1 by a wide margin.”  EPA was also aware that the incidents reported to the manufacturer significantly underestimated the scope and number of actual adverse impacts on both pets and humans.

Finally, in 2023, under pressure from threatened legal action by NGOs, a scathing Congressional investigation, and a new probe its own Inspector General (IG), EPA undertook a new review of Seresto pet collar-related incident reports.

However, this 2023 review concluded that Seresto pet collars meet EPA standards and would remain on the market. This time around, EPA took some steps, but they were minimal, such as adding label warnings on adverse effects along with instructions to remove the collar if they occur. It also required the manufacturer to include more information in its incident reports to EPA. These were all actions to which the manufacturer did not object.

The subsequent IG report was quite critical, taking EPA to task for its continuing lax approach and recommended that, as a first step, EPA make “written determinations on whether the Seresto pet collar poses unreasonable adverse effects in pets, [including] an explanation of how the Office of Pesticide Programs came to its determinations.” Further, the IG recommended that EPA solicit and reply to “public comment by placing these documents in the applicable registration review dockets.”

In response, EPA told its Inspector General to go pound sand:

“As this was not a registration review action, OPP did not follow the procedural steps of the registration review process, nor did it place the documents in the registration review docket or make them available for public comment…Overall, OPP determined that, with the mitigation measures, the use of these collars would meet EPA’s standards of no unreasonable adverse effects under FIFRA [the Federal Insecticide, Fungicide, and Rodenticide Act].”

The IG dryly noted that “the Agency did not provide a detailed rationale for this statement, nor did it provide any support for the allowance of an equivalent alternative to a registration review under FIFRA.”  However, the IG has no power to force implementation of its recommendations, no matter how outrageous EPA’s conduct is.

By law, EPA is responsible for ensuring that all pesticides, including flea and tick products, sold in the United States do not cause unreasonable adverse effects when used according to label directions. In this instance, EPA has been grossly derelict in this basic duty.

Unfortunately, this blatant disregard is common in EPA decision-making about pesticide approvals or in conducting risk assessments for new chemicals. EPA exhibits unmistakable regulatory capture by the pesticide and chemical industries.

In this arena, the agency acts in the public interest only when compelled to by litigation. A seismic change in its basic posture is long overdue because we cannot continue to let it keep poisoning us – and our pets.


Kyla Bennett is PEER’s Director of Science Policy and the Director of PEER’s New England/Mid-Atlantic field office. She is a scientist and attorney formerly with U.S. EPA.

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